Amyotrophic Lateral Sclerosis (ALS) is a devastating motor neuron disease with a 3-5 year survival rate and no disease-modifying therapies. TAR DNA-binding protein of 43kD (TDP-43) is a nuclear RNA and DNA binding protein that becomes abnormally aggregated in the brain and spinal cord of most ALS patients as well as a subset of dementia patients (frontotemporal lobar degeneration with TDP-43 pathology, or FTLD-TDP), placing ALS and FTLD-TDP within a spectrum of diseases known as TDP-43 proteinopathies. Although TDP-43 pathology has been implicated in disease onset and progression, little is known about how TDP-43 becomes aggregated leading to progressive neurodegeneration. My long-term goal is to uncover the pathogenic mechanisms that promote TDP-43 aggregation, which will provide insights for future therapies against these debilitating diseases. Post-translational modifications have been implicated in the progression of neurodegenerative diseases. Using my background in acetylation biology, I previously demonstrated that acetylation of the tau protein promotes tangle formation in Alzheimer's disease and related tauopathies (Nat Commun. 2011~2:252). I have now demonstrated that TDP-43 is subject to acetylation, thus highlighting a new TDP-43 modification that is potentially linked to ALS and related proteinopathies. The centra hypothesis of this proposal is to determine whether acetylation of TDP-43 promotes aggregation and neurodegeneration. To accomplish this goal, I will acquire expertise in neuropathology from the mentoring laboratory and analyze TDP-43 acetylation in ALS and FTLD-TDP post-mortem brain and spinal cord as well as TDP-43 transgenic mice characterized by TDP-43 pathology and neurodegeneration. To directly determine whether acetylated TDP-43 promotes disease, primary neuronal cultures and transgenic mice expressing acetylated TDP-43 will be evaluated for pathological hallmarks, toxicity, and neurodegeneration that recapitulate human TDP-43 proteinopathies. Having established the disease relevance of TDP-43 acetylation, the independent phase will utilize in vitro and cell-based approaches to investigate the biological significance of acetylation in causing impaired TDP- 43 binding to target genes and RNAs, leading to a TDP-43 loss of function. Finally, as an independent investigator, I will utilize K99 phase training in neurodegenerative disease to generate a mouse model of hyper-acetylated TDP-43 and determine the ALS phenotype in both brain and skeletal muscle. These innovative studies will highlight TDP-43 acetylation as a critical modification linked to the progression of ALS and related TDP-43 proteinopathies.